JP5877633B2 - Glass board slip - Google Patents

Description

  The present invention relates to a glass sheet interleaf made of a polyethylene resin foam sheet. In particular, the present invention relates to a glass sheet interleaf used for packaging, packing and the like of glass plates used for glass panels for various image display devices.

  Conventionally, a low-density polyethylene-based resin foam sheet is used to prevent damage to the surface and the like during packaging and transport of glass plates used in glass panels for image display devices such as liquid crystal displays, plasma displays, and electroluminescence displays. Is inserted between the glass plates, and the glass plates and the foamed sheets are alternately stacked.

  When the foam sheet is inserted between the glass plates, a suction arm or the like is usually used and is automatically inserted between the glass plates. However, in the process of automatically inserting between the glass plates, the foamed sheet is bent due to, for example, sagging of the foamed sheet, which may cause a paper feeding error. In order to prevent this trouble, there is a demand for a strong foam sheet with less drooping.

  Conventionally, a low density polyethylene-based resin foam sheet having a foaming ratio of about 15 to 40 times that is used is lightweight and excellent in buffering properties (Patent Document 1). However, due to the resin properties of the low density polyethylene resin itself, there is a limit to the strength of the stiffness when it is made into a foam sheet. There is room for improvement in the handleability of the interleaf paper for glass plates, and there is a demand for a foam sheet that is stronger.

  Moreover, the low density polyethylene-based resin foam sheet is likely to cause a periodic unevenness called corrugation and a wavy phenomenon of the entire foam sheet. When the foam sheet is used in the state where the foam sheets are stacked as a glass sheet interleaving paper, the foam sheet with the corrugation becomes bulky, and the storage space and the transport space become larger than necessary. There was a problem that.

  In addition, there is a polypropylene resin foam sheet as a foam sheet that has the same level of cushioning as the low density polyethylene resin foam sheet and is superior to the low density polyethylene resin foam sheet in terms of rigidity. Had the disadvantage of being inferior in cold shock resistance.

  On the other hand, if the main raw material is a high-density polyethylene resin, it is possible to give the foamed sheet sufficient rigidity due to its resin characteristics. However, it has been difficult to obtain a foam sheet having a small thickness and a high expansion ratio.

JP 2007-262409 A

  The applicant has a low-density polyethylene resin and a high-density polyethylene resin foam sheet that can be used as a substitute for thick paper sheets, container partition plates, and container thick containers. A polyolefin resin foam sheet having an apparent density of 60 to 350 g / L using a high density polyethylene resin was proposed (Japanese Patent Application No. 2009-150766, referred to as the prior application invention). Although the polyolefin resin foam sheet of the prior invention can be sufficiently used as a glass sheet interleaf, a sheet having a lower apparent density is required depending on applications.

  The present invention has a thin thickness, low apparent density, light weight, excellent cushioning properties, strong stiffness, and good handling as a glass plate interleaf. The purpose is to provide paper.

In order to achieve the above object, the following invention was made. That is, the present invention
[1] It consists of a polyethylene-based resin foam sheet having a thickness of 0.2 to 1.5 mm, an apparent density of 20 g / L or more and less than 60 g / L, and a basis weight of 10 to 50 g / m ² , and the thickness direction of the foam sheet An average number of air bubbles is 1.4 or less, and the flexural modulus of the resin constituting the foamed sheet is 300 MPa or more.
[2] The interlayer paper for glass plate according to the above [1], wherein the polyethylene resin foam sheet has a peeling voltage of 0.4 kV or less.
[3] The glass sheet interleaf according to the above [1] or [2], wherein the crystallization temperature of the resin constituting the polyethylene resin foam sheet is 110 to 120 ° C.
[4] The glass plate according to any one of [1] to [3], wherein a melt tension at a crystallization temperature of + 15 ° C. of the resin constituting the polyethylene resin foam sheet is 20 cN or more. Interleaf.
[5] The above [1] to [4], wherein the resin constituting the polyethylene-based resin foam sheet has a crystallization temperature of + 15 ° C. and a melt viscosity of 2000 to 10,000 Pa · s at a shear rate of 13 sec ⁻¹ . The interleaf paper for glass plates according to any one of the above.
[6] The resin constituting the polyethylene resin foamed sheet contains a polymer type antistatic agent, and the blending amount of the polymer type antistatic agent is 2 to 25 parts by weight with respect to 100 parts by weight of the polyethylene resin. The glass sheet interleaf according to any one of the above [1] to [5], wherein
[7] A polyethylene-based resin layer is laminated on at least one surface of the polyethylene-based resin foam sheet, and the resin constituting the resin layer contains a polymer-type antistatic agent. The glass sheet interleaf according to any one of the above [1] to [5], wherein the blending amount is 5 to 120 parts by weight with respect to 100 parts by weight of the polyethylene resin constituting the resin layer. Is the gist.

  The interleaf paper for a glass plate of the present invention comprises a polyethylene resin foam sheet having a specific polyethylene resin, a specific apparent density, thickness and basis weight. By increasing the thickness, even if the apparent density is low and light, the stiffness is strong and the handleability as a glass sheet interleaf is good. In addition, since the polyethylene resin foam sheet constituting the interleaf paper for the glass plate of the present invention has less undulations, it is not bulky when the foam sheets are stacked or used as an interleaf paper between the glass plates. Efficiency is improved. Moreover, since the foamed sheet which comprises the interleaving paper for glass plates of this invention has visibility, handling property improves, such as being able to confirm a glass plate through the interleaving paper.

  Further, in the interleaf paper for glass plate of the present invention, an antistatic function is imparted by adding a polymer type antistatic agent to the foamed sheet constituting the interleaf paper for glass plate or the resin layer laminated on the foamed sheet. be able to. Thereby, the surface resistivity of the foamed sheet constituting the interleaf for glass plate is reduced, and there is an effect that dust or the like hardly adheres to the foamed sheet.

It is a cross-sectional enlarged photograph of the width direction of the foam sheet which comprises the interleaf for glass plates of this invention. It is explanatory drawing of the drooping measurement method of a foam sheet.

The polyethylene-based resin foam sheet used as the glass sheet interleaf of the present invention will be described.
The foam sheet constituting the interleaf paper for a glass plate of the present invention has a sheet thickness of 0.2 to 1.5 mm, an apparent density of 20 g / L or more and less than 60 g / L, and a basis weight of 10 to 50 g / m ^2. The average number of cells in the thickness direction of the foamed sheet is 1.4 or less, and the flexural modulus of the resin constituting the foamed sheet is 300 MPa or more. Moreover, it is preferable that the crystallization temperature of resin which comprises this foamed sheet is 110-120 degreeC. Furthermore, it is preferable that the melt tension of the resin constituting the foamed sheet at the crystallization temperature of the resin constituting the foamed sheet + 15 ° C. is 20 cN or more. Furthermore, it is preferable that the melt viscosity of the resin constituting the foamed sheet at a crystallization temperature of the resin constituting the foamed sheet + 15 ° C. and a shear rate of 13 sec ⁻¹ is 2000 to 10,000 Pa · s.

  The foam sheet which constitutes the interleaf paper for glass plate of the present invention has a sheet thickness of 0.2 to 1.5 mm. If the thickness of the foam sheet is too thin, the protection and buffering properties of the glass plate will be insufficient. On the other hand, when the thickness of the foam sheet is too thick, when the foam sheets are stacked as the interleaving paper, it becomes bulky, and the stacked thickness becomes too thick, so that the loading efficiency is impaired. Therefore, the thickness of the foam sheet is preferably 0.3 to 1.3 mm, more preferably 0.4 to 1.2 mm.

  The foamed sheet constituting the interleaf paper for the glass plate of the present invention has an apparent density of 20 g / L or more and less than 60 g / L. If the apparent density is too low, sufficient strength cannot be exhibited as a glass sheet interleaf. On the other hand, if the apparent density is too high, there is a risk that the buffering properties and protective properties required as a glass sheet interleaf will be lowered. From such a point, the upper limit of the apparent density of the foamed sheet is preferably 55 g / L. On the other hand, the lower limit is preferably 25 g / L, more preferably 30 g / L, and particularly preferably 35 g / L.

  The resin constituting the foamed sheet used in the interleaf paper for the glass plate of the present invention contains a polyethylene resin as a main component. As used herein, the main component is a polyethylene resin, and the foamed sheet constituting the glass sheet interleaving paper is 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight of the polyethylene resin. Particularly preferably, it means 90% by weight or more.

  Examples of the polyethylene-based resin include resins having an ethylene component of 50 mol% or more. Specifically, high-density polyethylene, low-density polyethylene, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer Polymers, linear low density polyethylene such as ethylene-4-methylpentene-1 copolymer, ethylene-octene-1 copolymer, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-propylene- Examples include butene-1 copolymers, and mixtures of two or more thereof.

As the resin constituting the foamed sheet used in the interleaf paper for the glass plate of the present invention, it is particularly preferable to use a high-density polyethylene resin as a main component. Moreover, it is preferable that the density of resin which comprises this foamed sheet is 930g / L-970g / L.
As used herein, the main component is a high-density polyethylene resin. The resin constituting the foamed sheet is a high-density polyethylene resin of 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight. % Or more content.

  Specifically, a resin consisting only of a high density polyethylene resin, or a high density polyethylene, an ethylene homopolymer such as a branched low density polyethylene, a linear low density polyethylene, or an ultra low density polyethylene, ethylene and carbon number 2 types blended with low-density polyethylene such as ethylene copolymer with 3 to 10 α-olefin (however, α-olefin component unit with 3 to 10 carbon atoms is more than 10 mol% and 50 mol% or less) The above mixture is preferably used as a resin constituting the foamed sheet. In particular, from the viewpoint of improving the brittleness of the foam sheet, it is preferable to use a mixture in which the low density polyethylene is blended as a resin constituting the foam sheet, and the blend amount of the low density polyethylene is 30% by weight or less. More preferably, it is preferably 20% by weight or less.

  The resin constituting the foamed sheet includes polypropylene resins, styrene resins such as polystyrene, elastomers such as ethylene propylene rubber, styrene-butadiene-styrene block copolymers, etc., as long as the objects and effects of the present invention are not impaired. It may be included. In that case, the content is preferably 30% by weight or less, more preferably 25% by weight or less, and particularly preferably 20% by weight or less. In addition, the resin constituting the foam sheet is, for example, a nucleating agent, an antioxidant, an antistatic agent, a surfactant, a bubble regulator, a heat stabilizer, a weathering agent, in a range that does not hinder the object effect of the present invention. It may contain functional additives such as ultraviolet absorbers and flame retardants, inorganic fillers and the like.

  Furthermore, the resin constituting the foamed sheet used in the interleaf paper for the glass plate of the present invention has a bending elastic modulus of 300 MPa or more. Preferably it is 400 MPa or more, More preferably, it is 500 MPa or more. When the bending elastic modulus is too low, the bending rigidity is lowered, the stiffness is insufficient, and the handleability may be lowered. On the other hand, the upper limit is preferably 2000 MPa, more preferably 1800 MPa, and still more preferably 1500 MPa. If the flexural modulus is too high, the buffering ability may be reduced. Examples of the resin that satisfies the bending elastic modulus include those containing high-density polyethylene as a main component.

  The method for measuring the flexural modulus is in accordance with JIS K7171 (1994), using a test piece having a thickness of 2 mm × width of 25 mm × length of 40 mm, a span distance of 30 mm, an indenter radius R1 of 5.0 mm, a support base The measured value is measured under the condition of the radius R2 of 2.0 mm and the test speed of 2 mm / min. In addition, as a test piece of resin constituting the foam sheet, the foam sheet (in the case of the foam sheet provided with the resin layer, the resin layer is removed) is defoamed using a heating press and a cooling press. A non-foamed resin, and a plurality of the non-foamed resins are stacked to obtain a non-foamed resin sheet having the thickness of the test piece described above using a heating press and a cooling press. Use what is cut out.

The excellent rigidity in the foam sheet constituting the glass sheet interleaf of the present invention is mainly that the bending elastic modulus of the resin constituting the foam sheet is 300 MPa or more, and the average number of cells in the thickness direction of the foam sheet is It is manifested by a combination of configurations of 1.4 or less. That is, a foam sheet having an average number of bubbles in the thickness direction of 1.4 or less has a high thickness because the foam film has a large thickness in consideration of the apparent density of the foam sheet. Furthermore, by using a polyethylene-based resin in which the flexural modulus of the resin constituting the foamed sheet is 300 MPa or more, the foamed sheet is strong.

  The lower limit of the number of bubbles in the thickness direction of the foamed sheet is generally about 0.8 or more although it is related to the apparent density, thickness and basis weight of the foamed sheet. In addition, when the number of bubbles in the thickness direction of the foam sheet is less than one, a concave portion where no bubbles exist is formed on a part of the surface of the foam sheet, and surface properties (thickness accuracy of the foam sheet) And the appearance and strength may be reduced. From the above viewpoint, the lower limit of the number of bubbles in the thickness direction of the foamed sheet is preferably 0.9, and more preferably 1. On the other hand, if the upper limit of the number of bubbles exceeds 2, it may be difficult to maintain the strength of stiffness.

Furthermore, the foamed sheet constituting the glass sheet interleaf of the present invention has visibility and can be seen through the interleaf. This visibility is manifested when the average number of bubbles in the thickness direction of the foam sheet constituting the glass sheet interleaf is 1.4 or less. In the conventional foam sheet, since the number of cells in the thickness direction is large, it is difficult to obtain a foam sheet having visibility. When the interleaving paper for glass plate of the present invention is used, when the interleaving paper is arranged on the glass plate, the handling property is improved, for example, the state of the glass plate can be confirmed through the interleaving paper.

  In the present invention, the measurement of the number of bubbles in the thickness direction of the foamed sheet determines 10 measurement points at equal intervals in the width direction over the entire width of the foamed sheet. The number (number) of bubbles in the thickness direction at the measurement location is obtained, and the arithmetic average value of the number of bubbles in the thickness direction at each measurement location is defined as the number (number) of bubbles in the thickness direction in the present invention. In addition, the number of bubbles in the thickness direction of each of the above measurement points was taken by taking a foam sheet width direction cross-sectional photograph in which the measurement points were magnified 100 times, and a straight line was drawn in the thickness direction of the foam sheet on the obtained photograph. This value is obtained by counting all the number of bubbles that intersect. In addition, in the cross-sectional enlarged photograph, when fine bubbles that are clearly different from the bubbles occupying most of the photograph are seen, the fine bubbles are not counted as the number of bubbles.

In this invention, the basic weight of the foamed sheet which comprises the paper sheet for glass plates is 10-50 g / m < ² >. If the basis weight is too small, the strength of the stiffness may not be sufficiently exhibited. On the other hand, if the basis weight is too large, the handleability is lowered and the cost is increased. The basis weight of such a point, preferably 15~45g / ^{m 2,} more preferably from 20 to 40 g / ^{m 2.}

The basis weight is measured by cutting out a test piece having a thickness of 25 mm long × 25 mm wide × foamed sheet from the foamed sheet, measuring the weight (g) of the test piece, multiplying the weight by 1600, Basis weight (g / m < ² >) can be calculated | required by converting into a unit.

  It is preferable that the crystallization temperature of the resin constituting the foam sheet used in the interleaf paper for the glass plate of the present invention is 110 to 120 ° C. By satisfying the above range, the foam sheet is more rigid and firm. The crystallization temperature is closely related to the foam moldability at the extrusion foaming temperature when producing a highly foamed foam sheet having a thin sheet thickness. As resin which comprises the foamed sheet whose crystallization temperature is the said range, what has a high density polyethylene-type resin as a main component is mentioned.

  The crystallization temperature of the resin constituting the foamed sheet can be determined from a DSC curve obtained by heat flux differential scanning calorimetry based on JIS K7121 (1987).

  Specifically, 2 to 4 mg of a sample cut out from the foam sheet was collected, and heated from 23 ° C. to 200 ° C. at a heating rate of 10 ° C./min using a heat flux differential scanning calorimeter, and this temperature was maintained for 10 minutes. After being kept, it can be measured by cooling to 30 ° C. at a cooling rate of 10 ° C./min. At this time, in the DSC curve obtained during cooling, the temperature at the top of the exothermic peak due to crystallization is defined as the crystallization temperature (CP). When two or more exothermic peaks due to crystallization appear, the vertex temperature of the crystallization peak having the largest area is defined as the crystallization temperature.

  The melt tension of the resin constituting the foamed sheet at the crystallization temperature of the resin constituting the foamed sheet + 15 ° C. is preferably 20 cN or more. If the melt tension at the crystallization temperature + 15 ° C. of the resin constituting the foamed sheet is 20 cN or more, it is possible to more easily prevent bubbles from being broken during extrusion foaming and maintain the foam shape. Therefore, it is possible to more easily obtain a foam sheet having a low apparent density in which the number of bubbles in the thickness direction is controlled to 2 or less, and undulation is suppressed. The condition of crystallization temperature + 15 ° C. corresponds to the extrusion foaming temperature when obtaining the foamed sheet.

  In the present invention, examples of the polyethylene-based resin from which a foamed sheet that satisfies the above-described melt tension requirements are obtained include commercially available polyethylene manufactured by Tosoh Corporation (grade name: 08S55A).

  The melt tension at the crystallization temperature + 15 ° C. of the resin constituting the foamed sheet of the present invention can be measured, for example, by a melt tension tester type II manufactured by Toyo Seiki Seisakusho as follows.

Specifically, using a melt tension tester having an orifice having an orifice diameter of 2.095 mm, a length of 8 mm, and a cylinder having a diameter of 9.55 mm, the temperature of the resin charged in the cylinder is determined in advance by the above-mentioned heat flux differential scanning calorific value. After controlling the resin crystallization temperature obtained by measurement using a meter to + 15 ° C. and allowing it to stand for 4 minutes, the molten resin in the cylinder was pushed in by a piston at a speed of 10 mm / min and installed at the bottom of the cylinder Extruded into a string from the orifice. After this string-like object is hung on a tension detection pulley having a diameter of 45 mm, the take-up speed is increased to 15.7 m / s at an acceleration of about 1.3 × 10 ⁻² m / s ² and the melt tension is measured. . In addition, when it does not reach 15.7 m / s and the string-like object is cut, it is a measured value at the take-off speed at the time of cutting.

  When the melt tension of a string-like object detected by a detector connected to a tension detection pulley is measured over time, the chart shows the melt tension (cN) on the vertical axis and time (seconds) on the horizontal axis. A graph with amplitude is obtained. Next, the median value (X) of the amplitude of the stable portion is taken. In the present invention, this value (X) is the melt tension. In the measurement, a specific amplitude that occurs infrequently is ignored. When preparing a sample for measuring the melt tension of the resin constituting the foamed sheet, the foamed sheet is heated in a vacuum oven and defoamed, and the defoaming condition in the vacuum oven at that time is the foamed sheet. It can measure by making it the temperature more than melting | fusing point of the polyethylene-type resin which comprises, and making it the state under pressure reduction.

Moreover, it is preferable that the melt viscosity of the resin which comprises the said foam sheet in the crystallization temperature +15 degreeC of the resin which comprises the said foam sheet, and the shear rate of 13 sec < ^-1 > is 2000-10000 Pa.s. If the crystallization temperature of the resin constituting the foamed sheet is + 15 ° C. and the melt viscosity at a shear rate of 13 sec ⁻¹ is within the above range, the foaming agent is not separated and dissipated from the foamable molten resin in the extruder, A foam sheet having a low apparent density can be obtained more easily. The melt viscosity is preferably 2500 to 8000 Pa · s, more preferably 3000 to 7000 Pa · s, and still more preferably 3000 to 5000 Pa · s.

  The melt viscosity can be measured by, for example, Capillograph 1D manufactured by Toyo Seiki Seisakusho. The crystallization temperature of the resin constituting the foamed sheet can be determined from a DSC curve obtained by heat flux differential scanning calorimetry based on the above-mentioned JIS K7121 (1987).

Specifically, a capillograph 1D having an orifice hole diameter of 2.095 mm, a length of 8 mm, and a cylinder having a diameter of 9.55 mm is used, and the temperature of the resin charged in the cylinder is determined in advance by the above-described heat flux differential scanning calorific value. The temperature is controlled at a crystallization temperature of + 15 ° C. obtained by measurement using a meter, and after standing for 4 minutes, the molten resin in the cylinder is pushed in by a piston at a speed of 10 mm / min and installed at the lower end of the cylinder. The cord is extruded from the orifice. At this time, the viscosity can be calculated from the load applied to the piston. The condition of the shear rate of 13 sec ⁻¹ corresponds to the melt tension measurement condition. When adjusting the measurement sample of the resin that constitutes the foam sheet, the foam sheet is heated in a vacuum oven and defoamed, and the defoaming conditions in the vacuum oven at that time constitute the foam sheet. The temperature is equal to or higher than the melting point of the polyethylene resin and the pressure is reduced.

  The tensile breaking elongation of the resin constituting the foamed sheet is preferably 10 to 150%. If it is in the said range, the tear which generate | occur | produces in a foam sheet at the time of extrusion foaming can further be prevented. From the above viewpoint, it is preferably 15 to 130%, more preferably 20 to 100%.

  The measurement method of the tensile elongation at break is measured according to the measurement method of the tensile elongation at break of JIS K7127 (1989) using a sample of a No. 2 type test piece having a thickness of 1 mm according to JIS K7127 (1989). . In this case, the sample was allowed to stand for 24 hours under conditions of 23 ° C. and 50% humidity, and then a tensile test was performed at a test speed of 500 mm / min. The value divided by the distance 25 mm is calculated. The above measurement is performed 5 times, and the arithmetic average value of the obtained tensile breaking elongation is adopted. When adjusting the measurement sample of the resin that constitutes the foam sheet, the foam sheet is heated in a vacuum oven and defoamed, and the defoaming conditions in the vacuum oven at that time constitute the foam sheet. It can be measured by setting the temperature at a temperature equal to or higher than the melting point of the polyethylene-based resin under reduced pressure.

In the foam sheet constituting the interleaf paper for the glass plate of the present invention, the surface resistivity of the foam sheet is set to 1 × 10 ⁷ to 1 × 10 ¹⁴ Ω / □ by adding a polymer type antistatic agent. Can do. If the surface resistivity is within the above range, sufficient antistatic properties can be obtained, and it is difficult for dust to adhere to the surface of the foamed sheet, making it more suitable as a glass sheet interleaf. From the above viewpoint, the surface resistivity is preferably 5 × 10 ¹³ Ω / □ or less, and more preferably 1 × 10 ¹³ Ω / □ or less.

  The surface resistivity in the present invention is measured according to JIS K6271 (2001) after adjusting the condition of the following test piece. That is, a test piece cut out from a foamed sheet as a measurement object (length 100 mm × width 100 mm × thickness: thickness of measurement object) was allowed to stand for 36 hours in an atmosphere at a temperature of 20 ° C. and a relative humidity of 30%. Condition adjustment is performed, and the surface resistivity is measured after a lapse of 1 minute from the start of voltage application under the condition of an applied voltage of 500 kV.

In order to set the surface resistivity of the foamed sheet to 1 × 10 ⁷ to 1 × 10 ¹⁴ Ω / □, the blending amount of the polymer antistatic agent of the resin constituting the foamed sheet is a polyethylene-based material constituting the foamed sheet. It is preferable that it is 2-25 weight part with respect to 100 weight part of resin. If it is in the said range, desired antistatic performance can be exhibited, and foaming will not be hindered. From this viewpoint, the blending amount of the polymer antistatic agent is preferably 3 to 20 parts by weight, and more preferably 4 to 15 parts by weight.

  The number average molecular weight of the polymeric antistatic agent is 2000 or more, preferably 2000 to 100,000, more preferably 5000 to 60000, and particularly preferably 8000 to 40000. Therefore, the antistatic agent is a polymer type antistatic agent that is distinguished from an antistatic agent comprising a surfactant. The upper limit of the number average molecular weight of the polymer type antistatic agent is approximately 1,000,000. By setting the number average molecular weight of the polymer type antistatic agent within the above range, it is possible to prevent the antistatic agent from transferring to the glass plate and contaminating the glass plate surface.

  In addition, the said number average molecular weight is calculated | required using high temperature gel permeation chromatography. For example, when the polymer type antistatic agent is a hydrophilic resin mainly composed of polyetheresteramide or polyether, the sample concentration is 3 mg / ml using orthodichlorobenzene as a solvent, and the column temperature is 135 ° C. using polystyrene as a reference substance. It is a value measured under the conditions. In addition, the kind of the said solvent and column temperature are suitably changed according to the kind of polymeric antistatic agent.

The polymer type antistatic agent used in the present invention has a volume resistivity of 10 ⁵ to 10 ¹¹ Ω ·
A copolymer of a hydrophilic resin of cm and a polyolefin may be mentioned. Examples of the hydrophilic resin include polyether diols, polyether diamines, polyethers such as modified products thereof, polyether ester amides having polyether diol segments as polyether segment forming components, and poly ethers as polyether segment forming components. Polyether amide imide having ether diol segment, polyether ester having polyether diol segment as polyether segment forming component, polyether amide having polyether diamine segment as polyether segment forming component, polyether segment forming component Polyether-containing hydrophilic resins such as polyether urethane having polyether diol or polyether diamine segments, nonionic A cationic polymer having 2 to 80, preferably 3 to 60, cationic groups separated by a child chain in the molecule, and a dicarboxylic acid having a sulfonyl group and a diol or polyether as essential constituent units, and An anionic polymer having 2 to 80, preferably 3 to 60 sulfonyl groups in the molecule can be used.

In addition, as a polymer type antistatic agent, in order to improve the compatibility with the polyethylene-based resin, give an excellent antistatic effect, and obtain an effect of suppressing the deterioration of physical properties due to the addition of the antistatic agent, polyethylene Preferred is a block copolymer of the same type or highly compatible resin as the base resin. For example, a polyolefin block and a block of the hydrophilic resin having a volume resistivity of 10 ⁵ to 10 ¹¹ Ω · cm are repeated. A block copolymer having a number average molecular weight (Mn) of 2000 to 60000 having an alternately bonded structure is exemplified. Among these, a block copolymer of polyether and polyolefin is preferable because it has excellent compatibility.

  The polyolefin block and the hydrophilic resin block have a structure in which the block is repeatedly and alternately bonded through at least one bond selected from an ester bond, an amide bond, an ether bond, a urethane bond, and an imide bond.

  The polyolefin block of the copolymer that is preferably used as a polymer antistatic agent is preferably a polyolefin having a carboxyl group at both ends of the polymer or a polyolefin having a carbonyl group at one end of the polymer.

Examples of the polymer antistatic agent as described above include compositions described in JP-A-3-103466 and JP-A-2001-278985. The composition described in JP-A-3-103466 includes (I) a thermoplastic resin, (II) polyethylene oxide or a block copolymer containing 50% by weight or more of a polyethylene oxide block component, and (III) the above (II In the composition of JP-A-2001-278985, the block of polyolefin (a) has a volume resistivity of 1 × 10 ⁵ to 1. A block copolymer having a number average molecular weight (Mn) of 2000 to 60000 having a structure in which blocks of a hydrophilic resin (b) of × 10 ¹¹ Ω · cm are alternately and repeatedly bonded. The block (a) and the block (b) have a structure in which they are alternately and repeatedly bonded via at least one bond selected from an ester bond, an amide bond, an ether bond, a urethane bond, and an imide bond. is there. Such polymer type antistatic agents are commercially available under trade names such as “SD100” manufactured by Mitsui DuPont Polychemical Co., Ltd. and “Pelestat 300” manufactured by Sanyo Chemical Industries, Ltd.

In the foam sheet constituting the interleaf paper for glass plate of the present invention, a foam sheet (hereinafter sometimes referred to as a laminated foam sheet) in which a resin layer is laminated on at least one surface of the foam sheet can be used. By laminating the resin layer, the mechanical strength of the foam sheet is improved, and if the polymer type antistatic agent is blended in the resin layer, the blending amount is smaller than that in the foam sheet. Even in this case, the surface resistivity can be set to 1 × 10 ⁷ to 1 × 10 ¹⁴ Ω / □.

  Examples of the resin constituting the resin layer include a thermoplastic resin, specifically, a resin mainly composed of a polyolefin resin. The polyolefin resin is a resin containing 50 mol% or more of an olefin component. Examples of the polyolefin resin include a polyethylene resin and a polypropylene resin. Furthermore, as other resins and additives blended in the resin constituting the resin layer, the same ones as described above for the foamed sheet can be used. The foam sheet and the resin constituting the resin layer do not need to be the same, and can be employed in the category of the resin as long as they can be laminated. From the viewpoint of production stability, it is particularly preferable to use a polyethylene resin as the resin layer.

  Specifically, when a polyethylene resin layer is laminated on a foamed sheet and the resin constituting the resin layer contains a polymer type antistatic agent, 100 parts by weight of the polyethylene resin constituting the resin layer is added. On the other hand, the blending amount of the polymer type antistatic agent is preferably 5 to 120 parts by weight. If the blending amount is within the above range, sufficient antistatic properties can be exhibited. From this point of view, the amount of the polymeric antistatic agent added to the resin layer is more preferably 10 to 100 parts by weight, and still more preferably 10 to 55 parts by weight with respect to 100 parts by weight of the polyethylene resin constituting the resin layer. Parts by weight.

In the case of a foamed sheet in which a resin layer is laminated on the foamed sheet constituting the interleaf paper for the glass plate of the present invention, the basis weight of the resin layer is preferably 0.5 g / m ² or more per side, more preferably It is 0.7 g / m ² or more, more preferably 1.0 g / m ² or more. The method for measuring the basis weight of the resin layer is obtained by appropriately expanding the vertical cross section of the laminated foam sheet on which the resin layer is laminated with a microscope or the like, and measuring the thickness of the resin layer at 10 points in the width direction at equal intervals. The arithmetic average value of the obtained values is taken as the average thickness of the resin layer, and the average thickness is multiplied by the density of the base resin constituting the resin layer, and the basis weight (g / m ² ) of the resin layer is obtained by converting the unit. be able to. However, this method is limited to the case where the interface between the resin layer and the foamed sheet is clear. When the interface between the resin layer and the foamed sheet is unknown, the basis weight measurement is performed when the laminated foamed sheet is manufactured by coextrusion or extrusion lamination. From the discharge amount X [kg / hour], the width W [m] of the obtained laminated foamed sheet, and the length L [m / hour] per unit time of the laminated foamed sheet, the following formula (1) The basis weight [g / m ² ] can be determined. In addition, when laminating | stacking a resin layer on both surfaces of a foam sheet, the basic weight of each resin layer is calculated | required from the discharge amount of each resin layer.
(Equation 1)
Basis weight [g / m ² ] = [1000X / (L × W)] (1)
When a resin layer is provided by laminating films by thermal lamination, the basis weight of the resin layer corresponds to the basis weight of the known film before lamination.

The polyethylene-based resin foam sheet constituting the interleaf paper for the glass plate of the present invention has few undulations, and does not become bulky when the foam sheets are stacked, and therefore has high transport efficiency during transportation. The foam sheet with less waviness is achieved by using a polyethylene-based resin having a flexural modulus of 300 MPa or more and controlling the average number of bubbles in the thickness direction to 1.4 or less.

  In addition, when the foam sheet is used as a slip sheet for a glass plate, when it is placed on the glass plate, movement of charges occurs at the interface between the slip sheet and the glass plate, and when the slip sheet is peeled off from the glass plate, Charges that have moved on the respective surfaces may remain and become charged (hereinafter, this phenomenon may be referred to as peeling charging). When this peeling electrification occurs, when the interleaf is peeled off from the glass plate due to static electricity due to the peeling electrification, dust or the like is likely to adhere to the glass plate, or trouble due to charging of the glass occurs. There is a fear.

The foam sheet constituting the interleaf paper for the glass plate of the present invention uses a polyethylene resin having a rigidity with a flexural modulus of 300 MPa or more, and the average number of bubbles in the thickness direction is 1.4 or less. When the foamed sheet is used as an interleaf for glass plates, the contact between the glass plate and the interleaf can be reduced, and the peeling charge can be reduced as compared with the prior art.
Moreover, peeling electrification can further be reduced by mix | blending a polymer type antistatic agent as mentioned above, and making the surface resistivity of a foamed sheet into the said range.

  Next, the manufacturing method of the polyethylene-type resin foam sheet which comprises the interleaf for glass plates of this invention is demonstrated. The foam sheet constituting the glass sheet interleaf of the present invention can be produced by extrusion foaming. For example, a foamed sheet is formed from a polyethylene-based resin that satisfies the above requirements and a polymer-type antistatic agent that is added as necessary (hereinafter, a polyethylene-based resin and a polymer-type antistatic agent that is blended as necessary). Is sometimes supplied to an extruder and melted by heating to obtain a resin melt. At this time, additives such as a bubble regulator can be added. Next, a physical foaming agent is press-fitted into the resin melt, and further kneaded to obtain a foamable resin melt for forming a foamed sheet. The foamable resin melt is adjusted to a foamable temperature in an extruder, and passed through an annular die. By extruding into the atmosphere, foaming the foamable resin melt to form a cylindrical foam, and cutting the inner surface of the cylindrical foam while taking it down while cooling along a cylindrical cooling device It can be obtained as a foam sheet. As the annular die, the extruder, the columnar cooling device, the device for opening the cylindrical foam, etc., known ones conventionally used in the field of extrusion foaming can be used. In addition, it is also possible to perform extrusion foaming using a flat die instead of the annular die.

  Examples of the physical blowing agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, and isohexane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, methyl chloride, and ethyl chloride. Organic physical foaming agents such as chlorohydrocarbons, fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, and inorganic systems such as oxygen, nitrogen, carbon dioxide, air and water Examples include physical foaming agents and decomposable foaming agents such as azodicarbonamide, and these may be used in combination. The above-mentioned physical foaming agents can be used in combination of two or more. Among these, an organic physical foaming agent is particularly preferable from the viewpoints of compatibility with a polyethylene resin and foaming properties, and among them, those mainly containing normal butane, isobutane, or a mixture thereof are preferable.

  The amount of physical foaming agent added can be adjusted according to the type of foaming agent and the desired apparent density. For example, in order to obtain a foamed sheet having the above density range using isobutane as a foaming agent, the amount of isobutane added is preferably 7 to 25 parts by weight per 100 parts by weight in total of the polyethylene resin and the polymer antistatic agent, Is 8 to 23 parts by weight, more preferably 9 to 20 parts by weight.

  As a main additive, a bubble regulator is usually added. As the bubble adjusting agent, either an organic type or an inorganic type can be used. Examples of the inorganic foam regulator include borate metal salts such as zinc borate, magnesium borate, borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium bicarbonate, and the like. Examples of the organic bubble regulator include sodium 2,2-methylenebis (4,6-tert-butylphenyl) phosphate, sodium benzoate, calcium benzoate, aluminum benzoate, and sodium stearate. A combination of citric acid and sodium bicarbonate, an alkali salt of citric acid and sodium bicarbonate, or the like can also be used as the bubble regulator. These bubble regulators can be used in combination of two or more. The addition amount of the cell regulator can be adjusted according to the target cell diameter. When talc is used, it is 0.1 to 2 parts by weight, preferably 1 to 1.5 parts per 100 parts by weight of the polyethylene resin. Parts by weight.

  As a method of controlling the number of bubbles in the thickness direction of the foam sheet to 2 or less, the amount of the bubble regulator is adjusted to be small, a lip having a parallel land is provided at the tip of the annular die, and the thickness direction of the foamable resin melt It is possible to adjust by extruding while holding down the expansion (swell). In addition, there is a method of controlling the number of bubbles in the thickness direction by inducing a slight amount of heat generation in the parallel lands while preventing the corrugation from occurring, and by connecting the bubbles.

  In the above method, in order to control the number of bubbles in the thickness direction of the foam sheet to be less than the amount that is normally used in order to control the number of bubbles in the thickness direction of the foam sheet, the dispersion state of the bubble modifier in the extruder is not good. There is a risk of becoming stable. If the dispersion of the foam control agent is non-uniform, the foam control agent is unevenly distributed in a part of the foam sheet, resulting in non-foaming and reduced buffering, or non-foamed concave portions on the foam sheet surface. May occur and the appearance may deteriorate. From the viewpoint of uniformly dispersing the air conditioner, the melt viscosity at the crystallization temperature + 15 ° C. of the resin constituting the foamed sheet is preferably within the above range.

  When laminating the resin layer on the foamed sheet, it can be produced by a method of laminating a film on the surface of the foamed sheet produced in advance by thermal lamination or a method of laminating by extrusion lamination. It can also be produced by a coextrusion foaming method. Among these methods, it is preferable to produce the foamed sheet by a coextrusion foaming method because the thickness of the resin layer can be reduced and the adhesive force between the resin layer and the foamed sheet can be further increased.

  The method of producing a laminated foam sheet by the coextrusion foaming method includes a method of coextrusion foaming into a sheet shape using a flat die for coextrusion and lamination, and a tubular laminated foam using an annular die for coextrusion. There are methods such as coextrusion foaming and then cutting a cylindrical foamed sheet into a sheet-like laminated foamed sheet. Among these, the method using an annular die for coextrusion is a preferable method because it can suppress the occurrence of the wavy phenomenon of the foam sheet and can easily produce a wide laminated foam sheet having a width of 1000 mm or more. is there.

When coextrusion is performed using the coextrusion die, an apparatus in which a foam sheet forming extruder and a resin layer forming extruder are connected to the coextrusion die is used.
First, as described above, a foamable resin melt is formed using a foam sheet forming extruder. At the same time, the resin layer forming resin and a polymer type antistatic agent added as needed to the resin layer forming extruder (hereinafter referred to as resin layer forming resin and polymer added as needed) The resin composition for forming the resin layer may be supplied together with the mold antistatic agent), heated, melted and kneaded, and then added with a volatile plasticizer and melt-kneaded as necessary to form the resin layer. Resin melt for use. A laminated foam sheet is obtained by co-extrusion of both.

  In the coextrusion method, it is preferable that a volatile plasticizer is added to the resin melt for forming a resin layer. As the volatile plasticizer, one having a function of lowering the melt viscosity of the resin melt for forming the resin layer and one that volatilizes from the resin layer and does not exist in the resin layer after the resin layer is formed is used. By adding a volatile plasticizer to the resin melt for forming a resin layer, the co-extrusion causes the temperature of the resin melt for forming the resin layer to approach the temperature of the resin melt for forming the foam sheet. (Temperature reduction effect) and the melt elongation of the molten resin layer can be remarkably improved (stretchability improvement effect). This makes it difficult for the foam structure of the foam sheet to be destroyed by the heat of the resin layer during extrusion foaming, and the elongation of the resin layer follows the elongation of the foam sheet when foamed. Is prevented.

  As a volatile plasticizer, it is 1 type selected from a C2-C7 aliphatic hydrocarbon and alicyclic hydrocarbon, C1-C4 aliphatic alcohol, or C2-C8 aliphatic ether. Alternatively, two or more types are preferably used. When a low volatile material such as a lubricant is used as a plasticizer, the lubricant or the like may remain in the resin layer and contaminate the glass surface of the package. On the other hand, the volatile plasticizer is preferable from the viewpoint that the resin of the resin layer is efficiently plasticized and the volatile plasticizer itself hardly remains in the obtained resin layer.

  Examples of the aliphatic hydrocarbon or alicyclic hydrocarbon having 2 to 7 carbon atoms include ethane, propane, normal butane, isobutane, normal pentane, isopentane, neopentane, cyclopentane, normal hexane, isohexane, cyclohexane, and normal heptane. Etc.

  Examples of the aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, normal butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol.

  Examples of the aliphatic ether having 2 to 8 carbon atoms include dimethyl ether, diethyl ether, propyl ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, methyl isopropyl ether, methyl butyl ether, methyl isobutyl ether, methyl amyl ether, methyl Examples include isoamyl ether, ethyl propyl ether, ethyl isopropyl ether, ethyl butyl ether, ethyl isobutyl ether, ethyl amyl ether, ethyl isoamyl ether, vinyl ether, allyl ether, methyl vinyl ether, methyl allyl ether, ethyl vinyl ether, ethyl allyl ether and the like.

  As the volatile plasticizer, those which are easily volatilized from the resin layer are used, and the boiling point thereof is preferably 120 ° C. or lower, more preferably 80 ° C. or lower. If the boiling point of the volatile plasticizer is within this range, if the laminated foam sheet obtained after co-extrusion is allowed to stand, volatilization occurs due to heat immediately after co-extrusion and further gas permeation at room temperature. The plasticizer is volatilized naturally from the resin layer and is naturally removed. The lower limit of the boiling point is approximately -50 ° C.

  The addition amount of the volatile plasticizer is preferably 7 parts by weight to 50 parts by weight with respect to 100 parts by weight in total of the resin for forming the resin layer and the polymer type antistatic agent added as necessary. . From the viewpoint of the temperature lowering effect and the stretchability improving effect, the amount of the volatile plasticizer added is preferably 9 parts by weight or more, and more preferably 10 parts by weight or more.

  On the other hand, if the addition amount of the volatile plasticizer is approximately 50 parts by weight or less, the physical property of the resin layer itself is not deteriorated, and the volatile plasticizer sufficiently penetrates into the resin melt for forming the resin layer. Since the volatile plasticizer is not ejected from the die lip, it is possible to sufficiently prevent the resin layer from being perforated and the surface from becoming uneven, so that the laminated foam has excellent surface smoothness. It becomes a sheet. From this viewpoint, the addition amount of the volatile plasticizer is preferably 40 parts by weight or less, more preferably 30 parts by weight or less, and further preferably 25 parts by weight or less. By making the addition amount of a volatile plasticizer into the said range, the extrusion resin temperature fall effect of the resin melt for resin layer formation at the time of co-extrusion and the extensibility improvement effect are ensured.

  Since the interleaf paper for a glass plate of the present invention is a specific foam sheet composed of the foam sheet produced as described above, the thickness is thin, lightweight and excellent in cushioning properties, and the stiffness is strong and handling. The property is good. In addition, about the said foamed sheet | seat, it can also be used not only as a sheet for glass plates but for other uses, such as a packing material and a shock absorbing material.

  Next, an Example and a comparative example are given and this invention is demonstrated concretely. However, the present invention is not limited to the scope described in the examples.

Examples 1 and 2 and Comparative Examples 2 and 4
As an extrusion apparatus for forming foam sheets, a first extruder having a screw diameter of 90 mm and a tandem extruder in which a second extruder having a screw diameter of 120 mm is connected to the downstream side of the first extruder are used. The apparatus which attached the cyclic | annular die | dye of 94 mm in lip diameter to the exit of the 2nd extruder was used.

  The resin of the kind shown in Table 1 and the amount of the polyethylene-based resin, and if necessary, the polymer-type antistatic agent shown in Table 1 (Pelestat 300 manufactured by Sanyo Chemical Co., Ltd., the amount of which is a polyethylene-based resin constituting the foam sheet) Of the tandem extruder, and a masterbatch containing the cell regulator shown in Table 1 (the amount added is 100 parts by weight relative to 100 parts by weight of the foamed sheet-forming resin composition). After supplying to the raw material inlet of one extruder and melt-kneading, it was set as the resin melt adjusted to 200 degreeC. Next, isobutane (addition amount is 100 parts by weight with respect to 100 parts by weight of the resin composition for forming a foam sheet) is press-fitted and kneaded into the resin melt, and is then added to the second extruder on the downstream side of the first extruder. Introduced into a foamable resin melt for forming a foam sheet, adjusted to the extrusion resin temperature shown in Table 1, and extruded into the atmosphere at a discharge rate of 100 kg / hr to foam the foamable resin melt for foam sheet formation. To obtain a cylindrical foam. The cylindrical foam was taken along a columnar cooling device (mandrel) having a diameter of 350 mm, and cut to open a foam sheet.

Examples 3-4 , Comparative Examples 1, 3, 5
The same tandem extruder as used in Example 1 was used as the foam sheet forming extruder. Further, a third extruder having a diameter of 50 mm and L / D = 50 was used as the resin layer forming extruder. The respective outlets of the second extruder and the third extruder were connected to an annular die for coextrusion so that the respective molten resins could be laminated in the annular die.

  Resin of the type and amount shown in Table 1, the polymer type antistatic agent of Table 1 added as needed, and the air conditioner shown in Table 1 (added amount is 100 parts by weight of resin composition for forming foam sheet) Was fed to the raw material inlet of the first extruder of the tandem extruder and melt-kneaded to obtain a resin melt adjusted to approximately 200 ° C. Next, isobutane (addition amount is 100 parts by weight relative to 100 parts by weight of the foamed sheet forming resin composition) is press-fitted into the resin melt and kneaded to be a second extruder on the downstream side of the first extruder. The foamed resin melt for forming a foamed sheet was introduced into a foamed resin melt, adjusted to the extrusion resin temperature shown in Table 1, and introduced into the annular die for coextrusion.

  On the other hand, the type and amount of resin for forming a resin layer shown in Table 1 and a polymer type antistatic agent added as necessary (Pelestud 300 manufactured by Sanyo Chemical Industries, Ltd., 100 weight of polyethylene resin constituting the resin layer) Part by weight), isobutane (11 parts by weight with respect to 100 parts by weight of the resin composition for resin layer formation) as a volatile plasticizer, supplied to a third extruder, melt-kneaded and resin for resin layer formation It was made into a melt, adjusted to the extrusion resin temperature shown in Table 1, and introduced into an annular die for coextrusion. Lamination composed of a resin layer / foaming layer / resin layer is formed by laminating and joining the resin melt for forming a resin layer on the outside and inside of the foamable resin melt for forming a foam sheet in an annular die for coextrusion. As a melt, it was extruded into the atmosphere (discharge amount of foamable resin melt for forming foam sheet 100 kg / hr, discharge amount of resin melt for forming resin 10 kg / hr) to form a cylindrical laminated foam. The extruded cylindrical laminated foam was taken off along a cylindrical cooling device (mandrel) having a diameter of 350 mm to open a foamed sheet in which resin layers were laminated. Table 2 shows the physical properties of the obtained foamed sheet.

The characteristics of the foam sheet were evaluated as follows. The results are shown in Table 3.
(Stackability evaluation)
The thickness from one end to the other end of the width of the foam sheet constituting the glass sheet interleaving paper obtained in the examples and comparative examples was measured using a thickness meter at a pitch of 10 mm, and the measured value It was confirmed that the difference between the maximum and minimum was within 0.2 mm. Next, 10 test pieces each having a width of 10 mm and a length of 25 mm were cut out in order from the position of 25%, 50%, and 75% of the full width from the sheet edge (a total of 100 mm in the foam sheet width direction). Since the foam sheet obtained in this example has a width of 1000 mm, a test with a width of 10 mm × a length of 25 mm is successively performed over a total of 100 mm in the width direction of the foam sheet from the positions of 250 mm, 500 mm, and 750 mm from the end. Ten pieces were cut out. By this operation, 10 samples (total of 30 samples) were cut out from the end portions at the positions of 250 mm, 500 mm, and 750 mm as base points. Then, the same operation was repeated 10 times to cut out a total of 300 samples. The cut out samples were combined into a bundle of 10 sheets each in the width direction, and 30 bundles of 10 sheets were used as measurement samples. Next, the stack height of each of the 30 measurement samples was measured. The obtained stack height was arithmetically averaged to obtain an average value. Subsequently, the standard deviation of the stack height of 30 measurement samples was obtained by calculation. The obtained standard deviation value was evaluated according to the following criteria.

Stackability evaluation criteria ◎: Standard deviation of stack height is 0.15 or less ○: Standard deviation of stack height is more than 0.15 and less than 0.2 ×: Standard deviation of stack height is 0.2 or more

(Peeling voltage)
The peeling voltage of the foam sheet constituting the glass sheet interleaf was measured as follows.
After pressure-bonding a foam sheet constituting a glass sheet and a glass plate of 40 mm × 40 mm in an atmosphere of 60 ° C. and 50% RH at a load of 130 kg / cm ³ for 18 hours, an atmosphere of 23 ° C. and 50% RH Under the condition, the foamed sheet was peeled off from the glass plate at a peeling speed of 50 m / min (peeling direction 180 °). It was measured. The peeling voltage was evaluated according to the following evaluation criteria.
(Double-circle): The peeling band voltage of a foam sheet is less than 0.2 kV (circle): The peeling band voltage of a foam sheet is 0.2 kV or more and 0.4 kV or less x: The peeling band voltage of a foam sheet exceeds 0.4 kV.

(Sag evaluation)
As a sample for measurement in the longitudinal direction, the extrusion direction of the obtained foam sheet and the length direction of the test piece were made to coincide with each other, and from the foam sheets obtained in Examples, Comparative Examples, or laminated foam sheets, width 25 mm × length 150 mm Five test pieces were cut out. Similarly, five test pieces in which the width direction of the obtained foam sheet and the length direction of the test pieces were matched were cut out.
As shown in FIG. 2, the cut-out test piece was placed on the base in a state of protruding 100 mm from the base end, and a weight was placed thereon and fixed. The distance from the tip of the test piece and the base end was measured. (When the sag does not sag, the measured value is 100 mm, and the lower the measured value, the greater the sag.) The value obtained by arithmetically averaging the measured data was defined as the sag amount.

First, the amount of sag was measured by the above method. In order to further consider the factor of thickness, the amount of sag was converted by the following method, and the evaluation was performed using the result.
(1) When the measured value was 100 mm (when there was no drooping), the data was adopted as it was, and the amount of drooping was calculated.
(2) When the measured value was 99 mm or less, the measured value was divided by the thickness, and the value was used as the amount of drooping conversion. However, when the converted droop amount exceeded 100 mm, the converted droop amount was set to 100 mm.

The amount of drooping conversion obtained by the above method was evaluated according to the following evaluation criteria.
○: Converted droop amount 40 mm or more ×: Converted droop amount less than 40 mm

Claims (7)

It consists of a polyethylene resin foam sheet having a thickness of 0.2 to 1.5 mm, an apparent density of 20 g / L or more and less than 60 g / L, and a basis weight of 10 to 50 g / m ² , and the number of cells in the thickness direction of the foam sheet A glass sheet interleaf made of a polyethylene-based resin foam sheet, wherein the average of the resin is 1.4 or less and the flexural modulus of the resin constituting the foam sheet is 300 MPa or more. 2. The glass sheet interleaving sheet according to claim 1, wherein the polyethylene resin foam sheet has a peeling voltage of 0.4 kV or less. The crystallization temperature of resin which comprises the said polyethylene-type resin foam sheet is 110-120 degreeC, The interlayer paper for glass plates of Claim 1 or 2 characterized by the above-mentioned. The glass sheet interleaving paper according to any one of claims 1 to 3, wherein the resin constituting the polyethylene-based resin foam sheet has a melt tension of 20 cN or more at a crystallization temperature of + 15 ° C. The crystallization temperature of the resin constituting the polyethylene resin foamed sheet is + 15 ° C., and the melt viscosity at a shear rate of 13 sec ⁻¹ is 2000 to 10,000 Pa · s, according to claim 1. Interleaf paper for glass plate. The resin constituting the polyethylene resin foamed sheet contains a polymer antistatic agent, and the amount of the polymer antistatic agent is 2 to 25 parts by weight based on 100 parts by weight of the polyethylene resin. The interleaf for glass plates according to any one of claims 1 to 5. A polyethylene resin layer is laminated on at least one surface of the polyethylene resin foam sheet, the resin constituting the resin layer contains a polymer antistatic agent, and the blending amount of the polymer antistatic agent is The glass sheet interleaf according to any one of claims 1 to 5, wherein the amount is 5 to 120 parts by weight with respect to 100 parts by weight of the polyethylene resin constituting the resin layer.